1. Field of the Invention
The invention relates generally to gravitationally stabilized peanut butter, and methods for preparing the same. More particularly, the invention relates to the use of chitosan to stabilize the oily and proteinaceous phases of peanut butter.
2. Background Art
In the manufacture of peanut butter, peanuts are first removed from the outer shells, then separated from the inner hulls. The peanut kernels are then roasted at a controlled temperature and moisture removed. The roasted peanuts are thereafter ground to a paste, the paste commonly being referred to as natural peanut butter. Such natural peanut butter is not stable: on standing, the natural peanut butter separates into a clear layer of peanut oil that gradually collects on top of a proteinaceous layer. Many consumers object to natural peanut butter for this reason, since they find it inconvenient to have to mix the peanut oil into the proteinaceous layer each time they wish to consume the peanut butter. Natural peanut butter also lacks the spreadability desired by consumers.
A stabilizing technique employed in the prior art to overcome this oil separation problem has been addition of hydrogenated peanut, soybean, cottonseed, rapeseed and/or palm oil, after the peanuts are ground, with thorough mixing. See, for example, U.S. Pat. No. 5,591,477, to Boyce, et al. This would set into a firm consistency matrix that entrapped the peanut butter. Musher, U.S. Pat. No. 2,131,064 disclosed a food base material that may be incorporated into peanut butter to maintain the peanut oil in suspension. The food base material comprised a heavy aqueous paste containing water-absorbent bodier and thickeners, such as pectin, and a relatively hard fat material. These stabilization techniques are subject to the objection, however, that ingestion of highly hydrogenated fats is widely regarded as presenting unacceptable risks to human health.
What is needed, therefore, and what the present invention provides, is a method to manufacture natural peanut butter that overcomes the oil separation problem and that is free from these objections. This is accomplished by mixing into the oil phase of natural peanut butter a quantity of chitosan and an edible fatty acid, blending the oil and proteinaceous phases, and adding water with stirring, as described below. Chitosan has been previously used as a food additive and in pharmaceutical preparations to reduce the absorption of lipids; see, for example, U.S. Pat. No. 4,223,023 to I. Furda. See generally, Hennen, William H., Ph.D., Chitosan, Woodland Publishing, Inc. (Pleasant Grove, Utah, 1996).
The use of chitosan to gravitationally stabilize peanut butter appears to be new, however.